It has recently been clarified that a nano polycrystalline diamond sintered object has hardness exceeding natural single-crystal diamond and has a property excellent as a tool. Hardness of the nano polycrystalline diamond sintered object is approximately from 120 to 130 GPa expressed in Knoop hardness. One example of such polycrystalline diamond is described, for example, in Japanese Patent Laying-Open No. 2003-292397 and Diamond and Related Materials, 15 (2006), pp. 1576 to 1579.
On the other hand, needs for a small tool and a tool having high wear resistance have increased, and a diamond material having higher hardness has been demanded.
In addition, it has been known that magnetic sensing can be carried out by making use of an NV (Nitrogen-Vacancy) center in the inside of diamond. For example, J. R. Maze et al., “Nanoscale magnetic sensing with an individual electronic spin in diamond,” Nature, Vol. 455, pp. 644 to 647 (2008) has made a report on magnetic sensing making use of an individual electron spin in diamond.
It has recently be clarified that a nano polycrystalline diamond sintered object has hardness exceeding natural single-crystal diamond and has a property excellent as a tool. Hardness of the nano polycrystalline diamond sintered object is approximately from 120 to 130 GPa expressed in Knoop hardness. One example of such nano polycrystalline diamond is described, for example, in Japanese Patent Laying-Open No. 2003-292397 and Diamond and Related Materials, 15 (2006), pp. 1576 to 1579.
In addition, needs for a small tool and a tool having high wear resistance have increased, and a diamond material having higher hardness has been demanded. One example of such a high-hardness diamond polycrystalline body is described, for example, in Japanese Patent Laying-Open No. 2007-55819.
On the other hand, reports paying attention to thermal conductivity of diamond have also been made. For example, J. Appl. Phys. 69 (12), 15 Jun. 1991, pp. 8122 to 8125 has made a report on thermal conductivity of an isotopically enriched polycrystalline diamond film, and Diamond and Related Materials, 1 (1992), pp. 717 to 726 has reported characteristics of diamond when isotopic composition is varied.